Sugarcane Top Borer

Sugarcane Top Borer

Moths are silvery white in colour having one black spot on each of the forewing. Larvae are -35 mm long, creamy white or yellow and brown head, devoid of stripes, with atrophied legs. The First two broods of this pest attack young plants. In subsequent generations, the pest attacks the terminal portion of the cane, causing Bunchy top. Third and fourth generations cause maximum damage. These plants are killed and there is total loss. The pest active during February to October.

Management

The pest population can be lowered down by collecting and destroying egg cluster

Remove dead hearts and destroy.

Varieties CoJ67, CoS767, Co1158 are less susceptible to top borer.

Intercropping with onion, methi, sauf and ajwain reduces the infestation of the pest.

Use Tricogramma japonicum @ 50,000 per hectare just after 60 days of planting 4 to 6 times at the interval of 10 days.

The economic threshold level of the pest in third brood is 6-7 percent incidence. So if the incidence of the pest increases more than this, use carbofuran 3 G @ 25 kg/ha or phorate 10 G @ 20 kg/ha and irrigate the crop.

The top borer (Scirpophaga excerptalis)is a major pest of sugarcane in sub-tropical India. It completes five generations (broods) in a year. First brood adult (moth) appears in February, second brood moth appears in April, the third brood in June, the fourth brood in August and the fifth in September. On an average 7-10 days are egg period and 7-10 days are pupal period and larval period is about 35-40 days. Thus, average brood period is around 54-60 days. The third generation (brood) which occurs in June and is more damaging as this attack takes place after completion of tillering and at starting of cane formation. The affected plants do not form good millable canes. The pest remains active from February to November and during winter months it hibernates as mature larva in the cane.

Amongst the borers of sugarcane, the moths of top borer are relatively easy to identify due to their silvery white colour which is distinctly different from straw coloured moths of other borers. Females have a tuft of crimson red/orange or buff colour anal hairs. Moths are nocturnal (emerge in night). However, top borer moths are often observed in the morning hours (cool hours) clinging on crown leaves of sugarcane. As day progresses moths take shelter in whorls / leaf sheath of sugarcane. Eggs are laid parallel to mid rib mainly on underside of younger crown leaves.

Egg mass is covered with orange tuft of anal hairs A female may lay 46-216 eggs. After about a week of incubation (7-10 days) hatching takes place. The fragile first instar larvae crawl actively on the leaves and bore into the mid- rib from the lower side of inner leaves of crown. Tunneling through the mid-rib larva finally reach the inner core of the crown and then enter the central core making hole through the unfolded leaves. These leaves show the larval damage as shot holes on unfolding. The mid-rib tunnel initially remains white and later turns reddish. Presence of the reddish mid-rib tunnel on the crown leaf indicates top-borer infestation.Larva eats away the growing point and thus slender dead heart is formed. As a result of fourth brood attack side shoots develop and give an appearance of bunchy top. Mature larvae tunnels through the cane downwards and reach towards the rind to make an exit hole and after making the exit hole closes it with the cut portion of rind. Behind the exit hole it also produces several silken discs for self protection. Second instar and onwards larvae are pale white to creamy, sluggish with atrophied legs. Pupa is cylindrical in shape and pale yellow in colour. Pupation takes place in the cane and pupal period lasts for about a week (7-10 days). Average life cycle is completed in 54-60 days.

Management

Installation of sex pheromone traps for monitoring and mass trapping of top borer moths,Collection and destruction of egg mass and dead hearts during 2nd brood period.

Application of carbofuran 3G @ 33 kg granules/ha or phorate 10 G @ 30 kg granules/ha in June (on the appearance of top borer moths as observed in traps). A light irrigation should be given after application of insecticide, if soil moisture is limiting.

Releases of Trichogramma japonicum @ 50,000 adults /ha at 7-10 days interval from July to check 4th and 5th broods.